Description

Meteorological assessment of wildfire risk has traditionally involved identification of several synoptic types empirically determined to influence wildfire spread. Such weather types are characterized by identifiable synoptic-scale structures and processes. Schroeder et. al. (1964) identified four recognizable synoptic-scale patterns that contribute most frequently to high fire danger over the Great Lakes Region. Two of these weather types, the Hudson Bay High, and the Northwest Canadian High, are regularly observed in conjunction with northwesterly flow at middle and upper tropospheric levels. Such synoptic-scale flow is often associated with the development of upper-level frontal zones and an attendant intrusion of stratospheric air into the troposphere. Properties of stratospheric air such as its high momentum, high values of potential vorticity and low water vapor content, can potentially contribute to fire danger and spread. It is also suggested that the high ozone mixing ratios often observed in the wake of wildfires may be the result of stratospheric intrusions. This paper will investigate the structure and physical processes associated with an upper-level front, which occurred in the vicinity of a documented fire, and propose a role for upper-frontal processes on wildfire behavior.